Transcript Abnormalities on structural images Findings and clinical

“Abnormalities” on structural images
Findings and clinical implications
Robert D. Zimmerman MD FACR
Weill Cornell Medical College
Definition
Incidental finding (IF)
“ A finding that has potential health or reproductive
importance discovered in the course of
conducting research but is beyond the aims of the
study”
• Wolf et al. Managing incidental findings in human
subjects research: analysis and recommendations. J
Law Med Ethics 2008: 36 219
Ifs encountered depend on
• Age of subject population
– Affects types of findings & their prevalence
• Imaging protocols used
– Study exam is not a clinical exam and therefore may not detect an
abnormality even if present
– If only perform anatomic T1 weighted sequence will fail to detect
processes that primarily alter tissue content rather than tissue volume
• Subclinical or asymptomatic processes
– Stable or slowly progressive processes
• How we (I) define IF
– Some findings are normal variants or so unlikely to be clinically
significant that are not worth mentioning
Population
•
•
•
•
422 studies reviewed since 2008
Subjects 5-20 years old
~ Mean approximately 15
No clinical neurologic abnormalities
IFs
20 subjects – 4.8%
• Aqueductal stenosis with “arrested” hydrocephalus - 1
• Middle fossa arachnoid cyst – 6
• Focal or diffuse enlargement of subarachnoid spaces and or
low brain volume – 3
• Chiari I malformation – 4
• Focal white matter abnormality - 1
• Cavum septum pellucidum – 3
• Intraventricular cyst – 1
• Suspected aneurysm - 1
Review of literature
• IF in 10-50% of subjects
– Pediatric subjects (2 studies) ~ 425 combined
• Incidence - 21%
• However > 50% had sinusitis
• Included pineal cysts and prominent perivascular spaces (normal
variants)
• Clinical f/u in 1/3
• Similar findings as in our population
– Adult and pediatric subjects
• 18% IF
– 2/3 sinus disease
– Aneurysm, 3 brain tumors
IF classification
• 1) Clinically significant
– Likely to need treatment
• Surgery, medical management
• 2) Potentially clinically significant
– Probably will not require clinical treatment but may need:
• Full diagnostic MR or other imaging test
• Referral to a neurologist or neurosurgeon
• Follow-up assessment to insure not a progressive process
• 3) Incidental finding not likely to require intervention
– Does patient need to know?
– Should there be follow-up imaging
Practical and ethical implications
• No consensus in US or Europe
• Are researchers obligated to look for and report IF?
– Researchers ~75%
– Subjects - > 95%
• What images should be reviewed by a neuroradiologist?
– Reactive – Only ask for review when researcher sees something
troublesome
– Proactive – Neuroradiologist reviews all images
– Very proactive – Include diagnostic sequences (e.g. FLAIR) even not
required for study design
IF
Type 1
• Aqueductal stenosis with hydrocephalus – 1
• Asymptomatic however likely to become
symptomatic over time
• Surgery
– Third ventriculostomy
IF
Type 3
•
•
•
•
•
•
Middle fossa arachnoid cyst – 6
Cavum septum pellucidum – 3
Intraventricular cyst – 1
Asymptomatic
Lesions usually static
No intervention necessary
– Probably should inform family of presence of arachnoid
cyst.
– Arachnoid cysts may rarely enlarge and become
hemorrhagic with head trauma
Arachnoid cysts
• Congenital lesions due to splitting of the inner and
outer layers of arachnoid
• Cells lining cyst secrete CSF
• Locations
–
–
–
–
Middle cranial fossa
Cerebral convexity
Suprasellar cistern
Posterior fossa
• Small and medium size cysts asymptomatic
• Large cysts may become symptomatic
– Treatment – Cyst fenestration
IF
Type 2
• Focal or diffuse enlargement of subarachnoid
spaces and/or low brain volume -3
• Chiari I malformation – 4
• Focal white matter lesion -1
• If static and asymptomatic no intervention
needed
• If progressive needs to be followed and/or
treated
White matter lesions
“UBO’s”
Ischemia
Trauma
Demyelination
???
Usually asymptomatic
Non-progressive
Chiari malformation
• Disclaimer – I hate Chiari Malformation
• Rant #1
• History
– 1891: Chiari (German not Italian) reported 4 types
– 1894: Arnold describes a single individual with meningomyelocoele
and mentioned in passing that the hindbrain is abnormal
– 1912 – Students of Arnold review the hindbrain anomalies in what is
now called Chiari II malformation and name them the “Arnold Chiari
malformation”
– Now – Term “Arnold Chiari” often used to describe all of these
malformations (Wikipedia)
• So Arnold gets credit because of 1 incompletely described case of Chiari II
and for all of the other malformations that he did not describe
Chiari malformation
•
•
•
•
Rant 2
At least 2 separate anomalies and maybe as many as 4
Chiari I completely separate from II-IV
Chiari II – Spina bifida
– Suite of brain & spinal cord abnormalities discovered at birth and now often in
utero
– Primary defect is failure to form cerebral ventricles at appropriate time leading
to small posterior fossa
– Genetic and/or nutritional
• Folic Acid deficiency
– Surgery to correct meningomyelocoele (in utero)
– Shunt for hydrocephalus
• Chiari III and IV very rare
– May be severe versions of Chiari II or separate diseases
• I have never seen a Chiari IV
Chiari I malformation
• Not a brain anomaly
• Not one thing
• Anomalies of the osseous cranio-vertebral junction and/or
posterior fossa
• Cerebellar tonsils “trapped” in the upper cervical spinal canal
leading to compression of the brain stem and altered CSF flow
– Secondary syringomyelia and/or hydrocephalus
• Any disorder that traps tonsils below foramen magnum will
present with similar clinical manifestations
Clinical manifestations
• Tussive and/or positional headache
• Signs of brain stem dysfunction
– Vertigo
– Nystagmus (abnormal eye movements)
– Lower cranial nerve dysfunction
• Syringomyelia
–
–
–
–
Loss of sensation of pain and temperature
Vibration and position
Eventual weakness and muscle atrophy
Insidious onset
• Hydrocephalus
• Treatment
– Surgical decompression of the skull base
– Shunt syrinx cavity and hydrocephalus
– Surgery halts progression but does not restore lost function
Imaging features
• Osseous abnormalities
–
–
–
–
Platybasia
Short clivus
Small volume posterior fossa
Assimilation of C1 into skull base
• Brain/CSF
–
–
–
–
Narrow craniovertebral junction CSF space
Tonsil and brain stem distorted and impacted into cervical spinal canal
Syringomyelia (cord cyst)
Hydrocephalus
• Tonsil more than 5 mm below foramen magnum
– Symptomatic Chiari usually > 10 mm
Rant #3
• It is hard to reliably measure tonsilar position
– Tonsils often off midline and asymmetric
– Precise definition of inferior margin of foramen
magnum difficult to determine
• Therefore very difficult to differentiate
between normal low lying tonsils (< 5 mm)
and mild Chiari I when no other abnormalities
• Don’t want to miss an asymptomatic Chiari I
since may slowly progress to irreversible
neurologic dysfunction
5-07-07
5-12-07
Neoplasms
• Brain neoplasms second most common
tumors in children (after leukemia)
• Many highly malignant acutely symptomatic
• Lower grade tumors
• Juvenile Pilocytic Astrocytoma
• Low grade (but malignant) astrocytoma
• Oligodendroglioma
• Pituitary adenomas
Incidental vascular abnormalities
• Aneurysm
– Out pouching of cerebral artery usually near base of brain
– Rupture leads to catastrophic intracranial hemorrhage
– However
• Small unruptured aneurysms (< 5 mm) typically don’t bleed
• Aneurysms rare in children and young adults
– Acquired not congenital lesions
• If suspect aneurysm on research study MRA can confirm or
exclude diagnosis and provide treatment guidance
Arteriovenous malformation (AVM)
• Congenital abnormal connection between arteries
and veins without intervening capillary bed
• Creates high flow “short circuit”
• Typically presents in young adults with intracerebral
hemorrhage or seizures
• Discovered incidentally in many individuals
undergoing MR for other reasons (e.g headache)
• Treatment
– Surgery with or without endovascular partial ablation if
presents with hemorrhage
– May treat or follow with imaging if no hemorrhage